A Compound Document is the W3C term for a document that combines multiple formats, such as XHTML, SVG, SMIL and XForms. The W3C Compound Document Formats (CDF) Working Group will specify the behaviour of some format combinations...
ripMIME has a single sole pupose, to extract the attached files out of a MIME package (as say produced by programs such as AMaViS, Inflex and Xamime). ripMIME deliberately has no other operating purpose (if you find another use, then that's great).
FLAC stands for Free Lossless Audio Codec, an audio format similar to MP3, but lossless, meaning that audio is compressed in FLAC without any loss in quality.